Printed circuit board components are available in many different types to control and regulate electrical flow through a particular circuit. Resistors, capacitors, diodes, transistors, and integrated circuits (ICs) are the most common of all components used in almost every electronic device, from a cell phone to a handheld radio. These components must be placed in strategic positions along the printed circuit board's (PCB) surface to create a useful electronic circuit.
A resistor is a tubular component that normally has specifically colored stripes along its outside surface. Its main purpose is to stop excessive electrical current from entering a circuit area; each resistor can stop only a certain amount of current, based on the component's resistance rating. The outside stripes signify a resistance value that assemblers reference when building a PCB. Improperly placed resistors can result in damage to other circuit board components from high current flows.
Capacitors resemble small cylinders that normally protrude from a PCB's surface. These printed circuit board components use the cylinder to store electrical current; the capacitor allows some current to trickle from the storage area to create a steady power supply to the rest of the PCB. The electronic device as a whole may not work correctly if the capacitors are improperly placed. As a result of bad or improperly placed capacitors, the electrical flow through the device's circuitry can have large variations that cause component failure.
Diodes secure the direction of electrical current flow through the printed circuit board components. Once current enters and exits the diode component, the electrical flow cannot reverse direction through the same diode. The component's internal design forms a barrier to reverse current flow; this roadblock is especially helpful for protecting sensitive microchips that can fail easily from excessive electrical flows.
Transistors are printed circuit board components that can either amplify electrical current or switch it to a different part of the circuit. They usually have three legs that attach to the PCB instead of the typical two-legged design. Electricity can be multiplied within the transistor and routed to a specific circuit region. It can also change the direction of the current flow to power a different circuitry area, such as when buttons are pressed on a television remote control.
Integrated circuits are essentially tiny PCBs within a small microchip. These square printed circuit board components have allowed electronic devices to become smaller since more circuitry can be contained in a smaller housing. As a result, remote controls and cellular phones have become progressively smaller over time.